Multiplex genome editing targeting soybean with ultra-low anti-nutritive oligosaccharides
Wenxin Lin, Huaqin Kuang, Mengyan Bai, Xiaomeng Jiang, Pengfei Zhou, Yinghua Li, Bo Chen, Huarong Li, Yuefeng Guan
Abstract
Soybean is the primary source of plant protein for humans. Owing to the indigestibility of the raffinose family of oligosaccharides (RFO), raffinose and stachyose are considered anti-nutritive factors in soybean seeds. Low-RFO soybean cultivars are generated by mutagenesis of RFO biosynthesis genes, but the carbohydrate profiles invite further modification to lower RFOs. This study employed a pooled multiplex genome editing approach to target four seed-specifically expressed genes mediating RFO biosynthesis, encoding three raffinose synthases (RS2, RS3, and RS4) and one stachyose synthase. In T1 progeny, rs2/rs3 and rs4/sts homozygous double mutants and a rs2/rs3/rs4/sts quadruple mutant (rfo-4m) were characterized. The rs2/rs3 mutant showed reduced raffinose and stachyose contents, but the rs4/sts mutant showed only reduced stachyose in seeds. The RFO contents in the rfo-4m mutant were almost eliminated. Metabolomic analysis showed that the mutation of four RFO biosynthesis genes led to a shift of metabolic profile in the seeds, including the accumulation of several oligosaccharides-related metabolites. These mutants could contribute to precision breeding of soybean cultivars for soy food production.